The planula stage of Aurelia.
Individual planula, less than 1 mm diameter, can be seen near the bottom edge of the photograph. In this species, the planulae are first brooded in the oral arms of the female medusa (see photo). After a short period of development, they enter the water column, and swim to find suitable hard substrate onto which they settle, and then metamorphose into a polyp.
Prepared by M. Dawson and K. Raskoff.